JP2008153244A - Electromagnetic cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively cool a heat generating member such as a switching element and to improve the design versatility of the main body interior. <P>SOLUTION: An electromagnetic cooker is provided with a plurality of induction heating coils that are installed on the lower surface of a top plate on which a plurality of cooking vessels can be mounted and that heat the plurality of respective cooking vessels; a plurality of inverters that are composed of positive and negative switching elements to output high-frequency currents to the plurality of respective induction heating coils; a heat dissipating member that is shared among the plurality of inverters to dissipate heat generated by the positive and negative switching elements; a cooling means that cools the heat dissipating member and the plurality of induction heating coils; and a control circuit that controls respective drivings of the switching elements. The heat dissipating member has a hollow structure; a plurality of fins are provided on the inner sides of facing sides thereof; the positive switching elements are attached on the outer surface of one facing side and the negative switching elements are attached on the outer surface of the other facing side; and a space between the plurality of fins is made a ventilating path of air from the cooling means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an electromagnetic cooker, and more particularly to an electromagnetic cooker intended to efficiently cool heating members such as induction heating coils and switching elements and to improve the degree of design freedom inside the main body. .

  In a conventional electromagnetic cooker, a plurality of substrates corresponding to a plurality of induction heating coils are arranged in multiple stages, and the degree of freedom in design is improved by efficiently cooling each drive circuit and each induction heating coil. (For example, refer to Patent Document 1).

JP 2002-33184 A (page 3-4, FIG. 1)

  In a conventional electromagnetic cooker, since a plurality of substrates are provided corresponding to each of the plurality of induction heating coils, it is difficult to set the output of each induction heating coil to an output exceeding the heat dissipation characteristics of the corresponding substrate. Met.

  The electromagnetic cooker according to the present invention solves the problems of the conventional electromagnetic cooker.

  An electromagnetic cooker according to the present invention includes a top plate on which a plurality of cooking containers can be placed, a plurality of induction heating coils provided on the lower surface of the top plate, for heating each of the plurality of cooking containers, An inverter composed of positive and negative switching elements, a plurality of inverters that output a high-frequency current to each of the plurality of induction heating coils, and a plurality of inverters that are common to the plurality of inverters One heat dissipating member that dissipates heat generated by the positive and negative switching elements, cooling means for cooling the heat dissipating member and the plurality of induction heating coils, and a control circuit for controlling the driving of each of the switching elements, The heat dissipating member has a hollow structure, and a plurality of fins are provided on the inner sides of the opposing side surfaces, and a front surface is provided on one outer side surface of the opposing side surfaces. A positive switching element is attached, the negative switching element is attached to the other outer surface, and an air blowing path from the cooling means is provided between the plurality of fins provided on the inner side of the opposite side surfaces of the heat radiating member. It is what.

  According to the electromagnetic cooking device concerning the present invention, cooling of exothermic members, such as a switching element, can be performed efficiently.

Embodiment 1
FIG. 1 is a configuration explanatory view showing an example of an electromagnetic cooker according to the present invention. Hereinafter, the configuration of the electromagnetic cooker and the cooling mechanism will be described with reference to the drawings.
The electromagnetic cooker according to the present invention has two stove portions 14a and 14b for placing the cooker on a top plate 10 provided on the upper surface of the case. On the lower surfaces of the stove parts 14a and 14b, induction heating coils 11a and 11b (see FIG. 2) are provided corresponding to the respective stove parts. The induction heating coils 11a and 11b are controlled by the control unit 1 and have a predetermined amount of heat in accordance with the size of the cooker and the amount of cooking materials installed on the top plate surface corresponding to each induction heating coil. The output is adjusted to obtain. A control command is input to the control unit 1 from the operation unit 13 disposed on the front surface of the electromagnetic cooker. Further, the control unit 1 is provided with two inverters composed of a pair of positive and negative switching elements (IGBT: Insulated Gate Bipolar Transistor), and a heat radiating plate 3 for radiating the heat generated by these IBGTs. Is provided. Each of these two inverters corresponds to the induction heating coils 11a and 11b described above. Further, an air intake port from the outside is provided on the back surface of the electromagnetic cooker. When the blower fan 5 is operated, the air 6 is taken in from the outside, and the heat radiating plate 3 and the induction heating coils 11a and 11b are cooled. . The electromagnetic cooker is provided with a roaster unit 12 for grilling fish and the like separately from the above-described two stove units 14a and 14b, but a control unit corresponding to the two stove units 14a and 14b is provided. By combining the heat sinks corresponding to each IGBT together on one board, the degree of freedom in designing the internal space of the electromagnetic cooker is improved, and the roaster unit 12 can be expanded.

Fig.2 (a) is a top view which shows an example of a structure of the heat sink 3 in the control part 1 of the electromagnetic cooker concerning this invention.
The control unit 1 controls the two induction heating coils 11a and 11b, and two inverters are arranged to control each induction heating coil. Each of the two inverters is composed of a pair of positive and negative switching elements (IGBT). Specifically, the induction heating coil 11a is controlled by an inverter constituted by the IGBT 2a that is the positive side switching element and the IGBT 2b that is the negative side switching element, and the IGBT 2c that is the positive side switching element and the negative side switching element. Induction heating coil 11b is controlled by an inverter constituted by IGBT 2d as an element. Of the four IGBTs constituting these two inverters, IGBTs 2a and 2c, which are positive side switching elements, are attached to the heat radiating plate 3 via thermally conductive insulating sheets 7a and 7b. Of the four IGBTs constituting these two inverters, the negative side switching elements IGBTs 2b and 2d are directly attached to the heat sink 3.

  Thus, the reason why the IGBTs 2a and 2c on the positive side are attached to the heat sink 3 via the heat conductive insulating sheets 7a and 7b is as follows. That is, normally, the electrical grounding of the IGBT is taken through the heat sink, but when the positive and negative IGBTs constituting each inverter are electrically connected, electrical interference occurs between the two. Therefore, the positive and negative IGBTs constituting the pair need to be electrically separated, and such a configuration is adopted. Therefore, when the IGBT constituting the inverter is electrically grounded without using the heat sink, the heat conductive insulating sheets 7a and 7b are unnecessary.

  Moreover, what is necessary is just to provide a heat conductive insulating sheet in either one of the pair of positive / negative IGBT which comprises each inverter. Specifically, if a heat conductive insulating sheet is provided on either one of the IGBTs 2a and 2b and either one of the IGBTs 2c and 2d, the grounding of the pair of positive and negative IGBTs can be divided. Further, from the viewpoint of more reliably preventing electrical interference, a heat conductive insulating sheet may be provided on both sides of the IGBT constituting the positive and negative pair. As such a heat conductive insulating sheet, there is one in which fine particles of metal (<φ0.1 mm) with an insulating coating on the surface are interposed in Si rubber. For example, a rubber for heat radiation insulation (TC) from Shin-Etsu Silicone Co., Ltd. -A, TC-AG, TC-BG). In the present embodiment, a heat-insulating rubber TC-A made by Shin-Etsu Silicone Co., Ltd. having a thickness of 0.4 mm is used.

  FIG. 2B is a cross-sectional view taken along the line A-A ′ of FIG. The heat radiating plate 3 has a hollow or fin structure in order to increase the heat radiating efficiency, and is cooled by the air 6 blown by the blower fan 5 disclosed in FIG. , It will dissipate heat.

  The rated output of the induction heating coil is normally set to 2.4 kW. Therefore, in the conventional electromagnetic cooker, the heat sink with the 2.4 kW heat dissipation capacity is provided corresponding to each induction heating coil. Also in the present invention, the rated output of the induction heating coils 11a and 11b is set to 2.4 kW. Therefore, the heat sink 3 is provided with a heat dissipation capacity of 4.8 kW. Since this heat dissipation capacity corresponds to the conventional heat dissipation plate with 2.4kW heat dissipation capacity, the total heat dissipation capacity of the heatsink is the same as before and the size of the heatsink is the same. .

FIG. 4 is a diagram showing the configuration of the control circuit of the electromagnetic cooker according to the present invention. The circuit operation will be described below with reference to the drawings.
First, power 20 is input to the smoothing circuit 19 from an external power source. This power 20 is normally set to 4.8 kW. The electric power 20 input from the external power source is converted into direct current by the smoothing circuit 19 and output to the inverter 15 and the inverter 16. Therefore, the sum of the output of the inverter 15 and the inverter output does not exceed 4.8 kW. The inverter 15 is configured by the above-described IGBTs 2a and 2b, and the inverter 16 is also configured by the IGBTs 2c and 2d. These inverters 15 and 16 are for driving the corresponding induction heating coils 11a and 11b at a high frequency by converting the DC power sent from the smoothing circuit 19 into, for example, AC power of about 20 kHz. The gate drive signal generation circuit (control circuit) 18 controls the driving of the two inverters 15 and 16 so as not to exceed the heat radiation capacity of the heat sink 3 by the temperature sensor 17 installed on the heat sink 3. . For example, when the output of the inverter 15 is 2 kW, the output of the inverter 16 is adjusted within a range of maximum 2.8 kW. Conversely, when the output of the inverter 16 is 2 kW, the output of the inverter 15 is maximum. The output is adjusted in the range of 2.8 kW. As described above, if the output of one of the inverters is equal to or lower than the rated output within a short time (for example, about 5 to 10 minutes), the output of one of the inverters is less than the rated output. It becomes possible to make the output of the inverter more than the rated output. Such output adjustment is possible, without increasing the number of parts and the heat dissipation capacity of the heat sink, and without complicating the device configuration, when rapid heating is required at the initial stage of cooking, When it is desired to boil in a short time, it becomes possible to cook at a high output above the rated output, and the convenience of the electromagnetic cooker is improved. In addition, when using an electromagnetic cooker in the home, it is rare to use both of the two-burner stoves at the maximum output at the same time, and even with such a configuration, it seems that practical problems will hardly occur. .
In the above embodiment, the case where the heat radiating plate having the heat radiation capacity corresponding to the amount of power input from the external power source is described. However, for example, the power 20 input from the external power source is 4.8 kW. In some cases, the heat dissipation capacity of the heat dissipation plate may be 4 kW. In such a case, the temperature sensor 17 limits the total amount of heat radiation of the two inverters 15 and 16 to 4 kW or less.

Although the case where two induction heating coils are used has been described in the present embodiment, the number of induction heating coils is not limited to two, and may be three or more. For example, when there are three stove sections, three induction heating coils are required, and there are three corresponding inverters. In this case, only the switching elements constituting the two inverters may be placed on one heat sink, or all the switching elements constituting the three inverters may be grounded on one heat sink. Good. Even in such a configuration, the same effect as described above can be obtained by controlling so that the total amount of heat generated by the switching elements placed on the heat sink does not exceed the heat dissipation capacity of the heat sink. That is, in an electromagnetic cooker equipped with n induction heating coils (n is a natural number of 2 or more), the rated output of each induction heating coil L1, L2 --- Ln is P1, P2 --- Pn, respectively. Where W1 and W2 --- Wn are the outputs, H1 and H2 --- Hn are the heat dissipation amounts of the induction heating coils corresponding to these outputs, and Ht is the heat dissipation capacity of the heat sink. The output of the induction heating coil is adjusted so as to satisfy the relationship 2).
W1 + W2 + --- + Wn ≦ P1 + P2 + --- + Pn --- (1)
H1 + H2 + --- + Hn ≦ Ht ---- (2)
If the heat radiation amounts of the induction heating coils corresponding to the rated outputs P1, P2 --- Pn are h1, h2 --- hn,
h1 + h2 + --- + hn ≦ Ht ---- (3)
Thus, the heat dissipation capacity Ht of the heat sink is determined.
In addition, it is not preferable to use the output exceeding the rated output so much from the characteristics of the switching element, and it is usually preferable to suppress the increase to about 20%. From this viewpoint, it is preferable to satisfy the relationship of the following formula (4).
Wx ≦ 1.2Px (x is a natural number less than n) ---- (4)

  Needless to say, from the viewpoint of the heat dissipation efficiency of the heat sink 3, it is preferable to use the induction heating coil 11 a side corresponding to the inverter constituted by the IGBTs 2 a and 2 b close to the cooling fan 5 at a high output. However, if the control unit 1 is configured to switch between an induction heating coil corresponding to the inverter constituted by the IGBTs 2a and 2b and an induction heating coil corresponding to the inverter constituted by the IGBTs 2c and 2d, cooling is performed. The inverter constituted by the IGBTs 2a and 2b close to the fan 5 can increase the output on both the left and right stoves of the electromagnetic cooker, which is preferable because convenience in cooking is improved.

  Further, the time during which the inverter can be used at the rated output or higher is generally determined from the sum of areas determined by the load applied to the switching element and the time for applying the load. That is, when a load is suddenly applied to the switching element, the time during which the inverter can be increased to the rated output or less is shortened, and when the load is not applied suddenly, the time that can be maintained above the rated output is increased. . Therefore, the time during which each induction heating coil can be maintained at or above the rated output is actually determined in consideration of the characteristics (withstand voltage characteristics and life characteristics) of the IGBT that is the switching element.

  In this embodiment, an IGBT is used as a switching element constituting the inverter. However, the switching element is not limited to the IGBT, and is a so-called power semiconductor having a switching function such as a thyristor or a power MOSFET. Needless to say, it can be applied and has the same effect.

  As mentioned above, according to the electromagnetic cooking device concerning the present invention, a plurality of inverters corresponding to a plurality of induction heating coils are arranged on one board, and a heat sink corresponding to positive and negative switching elements which constitute these inverters is shared. In addition to being able to increase the degree of freedom of design inside the electromagnetic cooker, it is possible to adjust the output of multiple induction heating coils within the range that does not exceed the heat dissipation capacity of the heat sink, and to enlarge the device In addition, the output of the induction heating coil can be increased or decreased as necessary without increasing the number of parts, and an output exceeding the rated output can be achieved in a short time.

Embodiment 2
Fig.3 (a) is a top view which shows an example of a structure of the heat sink 3a and 3b in the control part 1 of the electromagnetic cooker concerning this invention.
Unlike the one disclosed in the first embodiment, the control unit 1 is the positive side of the four IGBTs 2a, 2b, 2c and 2d constituting the two inverters corresponding to the two induction heating coils 11a and 11b. IGBTs 2a and 2c and negative-side IGBTs 2b and 2d are provided on two different heat sinks 3b and 3a, respectively. Moreover, the heat sink 3a is connected to a ground line through an insulating circuit (not shown), and the heat sink 3b is directly connected to the ground line. By adopting such a configuration, each IGBT can be attached to the heat radiating plate without using a heat conductive insulating sheet, and electrical interference between the positive side IGBTs 2a and 2c and the negative side IGBTs 2b and 2d is effective. To be suppressed.

  FIG. 3B is a B-B ′ sectional view of FIG. The heat dissipating plates 3a and 3b are arranged separately so as to face each other, and are cooled by the air 6 blown by the blower fan 5 disclosed in FIG. .

  Under such a configuration, the outputs of the two induction heating coils 11a and 11b are adjusted as follows. That is, the four positive and negative IGBTs 2a, 2b, 2c, and 2d constituting the two inverters corresponding to the two induction heating coils 11a and 11b are usually inductive heating coils having a rated output of 2.4 kW as a positive and negative pair. Correspondingly, the positive and negative IGBTs share the output on the positive side and the output on the negative side for the time being. Therefore, the output of the induction heating coil carried by each IGBT is 2.4 kW. It can be considered that it is approximately half equivalent to 1.2 kW. Moreover, since the heat dissipation capacity of the heat sinks 3a and 3b is 2.4 kW, the total heat dissipation capacity is 4.8 Kw, which is the same as the conventional one.

  However, in the electromagnetic cooker according to the present invention, among the IGBTs corresponding to the two induction heating coils 11a and 11b, the positive IGBTs 2a and 2c and the negative IGBT 2b and 2d are provided on the same heat sink. When using for a short time (for example, about 5 to 10 minutes), if the output of one of the inverters is less than the rated output, as long as the IGBT is not destroyed or suddenly deteriorated, the other It becomes possible to make the output of the inverter more than the rated output. For example, by setting the output sharing of the positive and negative IGBTs 2a and 2b corresponding to the induction heating coil 11a to 1.4 kW each and the output sharing of the positive and negative IGBTs 2c and 2d corresponding to the induction heating coil 11b to 1 kW each, the induction heating coil The output of 11a can be 2.8 kW, and the output of induction heating coil 11b can be 2 kW. Such output adjustment is possible, without increasing the number of parts and the heat dissipation capacity of the heat sink, and without complicating the device configuration, when rapid heating is required at the initial stage of cooking, It is possible to effectively cope with the case where it is desired to boil in a short time, and the convenience of the electromagnetic cooker is improved.

It is a perspective view explaining the structure of the electromagnetic cooker concerning this invention. It is a structure explanatory drawing explaining the structure of the heat sink of the electromagnetic cooker concerning this invention. It is a structure explanatory drawing explaining the structure of the heat sink of the electromagnetic cooker concerning this invention. It is a figure explaining the structure of the control circuit of the electromagnetic cooker concerning this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Control part, 2a-2d Switching element, 3 Heat sink, 3a Negative side heat sink, 3b Positive side heat sink, 5 Cooling fan, 6 Wind direction, 7a, b Thermal conductive insulating sheet, 10 Top plate, 11, 11a 11b induction heating coil, 12 roaster, 13 operation unit, 14a, 14b stove unit, 15 inverter, 16 inverter, 17 temperature detector, 18 gate drive signal generation circuit, 19 smoothing circuit, 20 input power.

Claims (5)

A top plate on which a plurality of cooking containers can be placed;
A plurality of induction heating coils provided on the lower surface of the top plate for heating each of the plurality of cooking containers;
A plurality of inverters composed of positive and negative switching elements, each of which outputs a high-frequency current to each of the plurality of induction heating coils;
One heat dissipating member that radiates heat generated by the positive and negative switching elements constituting the plurality of inverters, which is shared with the plurality of inverters,
Cooling means for cooling the heat radiating member and the plurality of induction heating coils;
A control circuit for controlling the driving of each of the switching elements,
The heat dissipating member has a hollow structure, and a plurality of fins are provided inside the opposite side surfaces, the positive switching element is attached to one outer side surface of the opposite side surfaces, and the negative side is attached to the other outer side surface. The electromagnetic cooker which attaches the switching element of this and uses the space | interval of the several fin provided inside the said opposing side surface of the said heat radiating member as the ventilation path of the air from the said cooling means. The electromagnetic cooker according to claim 1, wherein the plurality of fins are provided horizontally with respect to a traveling direction of air flowing through the air passage. The electromagnetic cooker in any one of Claim 1 or 2 which arrange | positions the positive / negative switching element which comprises one inverter attached to the said heat radiating member symmetrically. The electromagnetic cooker of any one of Claims 1-3 which arrange | positions the said heat radiating member in the approximate center of the control part by which the said control circuit is arrange | positioned. The electromagnetic cooker according to any one of claims 1 to 4, wherein an operation unit that inputs a control command is provided in the control circuit, and air that has passed through the air blowing path is guided to the operation unit.

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